JP3238148B2 - Charge control based on solvation of liquid electrophotographic developer compositions - Google Patents

Abstract

A solvation-based method for charging toner particles in a liquid electrophotographic developer composition is provided. The method makes use of a material containing specific solvation sites which is incorporated into the resinous phase of the toner, and a charge director which is a metal salt, the metal, cationic component of which is effective to form a highly stable, "solvated" charged toner complex. Toner and developer compositions are also provided which make use of the novel solvation-based mode of charge direction.

Description

Description: TECHNICAL FIELD The present invention relates generally to the field of color electrophotography. More particularly, it relates to an improved method for controlling the charge of a liquid electrophotographic developer composition, and to novel toner and developer compositions made by this method.

BACKGROUND To prepare an image printed by electrophotography or "xerographic" methods, a selected temperament, ie, a photoconductive material such as selenium, is applied to an electrophotographic plate (typically made of metal, glass, or plastic). A non-conductive insulating material is applied and then the photoconductive surface becomes electrostatically charged, for example by ionization from a corona discharge. The optical image is then focused on the charged surface, and the illuminated area is discharged or reduced in potential, while the rest of the surface remains charged. Next, a visible image is obtained by applying an appropriate developer composition to the thus formed electrostatic image. The developer composition may be dry or liquid.

A conventional liquid developer composition is obtained by dispersing pigment particles in an insulating carrier liquid. When such a composition is applied to a substrate having an electrostatic image, the charged pigment particles migrate to the substrate surface and deposit on the surface in conformity with the electrostatic image. The developed image is then transferred to another substrate, such as paper. (In some cases, it is desirable to eliminate the intermediate step of image transfer, ie, to produce the developed image directly on the final surface; see, for example, Greig US Pat. No. 3,052,539).

Liquid developers used for developing multicolor images are relatively new and have a colorant embedded in a thermoplastic resin core. These "toner" particles are then dispersed in the insulating carrier medium described above. The same composition is used as in black-and-white electrophotography. These developer compositions further include "charge directors" or "charge control agents" to control the charge obtained by the toner particles in the insulating liquid.

When a color image is generated by electrophotography, the above-described charging, exposing, and developing steps are performed using toner of a color corresponding to each of the constituent colors of the image continuously and individually. In some color printing methods, each of the color images is transferred from the xerographic member to a print substrate after development and before forming the next color image. However, this method requires a very accurate registration of a continuous color image on the substrate to which the color image is to be transferred in order to obtain a good composite image.

Other color printing methods include the four-color liquid electrophotographic method currently in practical use, known as "consecutive color toning" or "continuous multicolor image development". The method comprises the steps of (1) charging a photoconductive ("pc") surface, (2) printing a first latent image on the surface by exposing through a colored transparency, (3) pc
In contact with a first color, typically yellow liquid developer composition, and (4) discharging the pc surface. These steps are then repeated sequentially, typically using magenta, cyan, and black developer compositions. That is, this circulation step is repeated until a color image is completed.

Electrophotographic coloring methods have a number of frequently encountered problems. These are unstable toners; stain the background,
I.e., toner adheres to uncharged non-image areas (a problem common to zinc oxide and other positive toner systems); low resolution (i.e., low edge acuity); Low image density due to insufficient deposition of the first image; and that the second processing color raises the first image in areas where a portion of the first image was to be discharged but not discharged. Includes "image" or "text" stains that result from coloring. Other problems with current electrophotographic color development methods include, for example, U.S. Pat. No. 4,701,3, by Alexandrovich et al.
As described in No. 87, multiple washing and drying steps may have to be performed during development. The inventors have proposed a solution in which the developed surface is cleaned with a polar solution after each developing step. It is suggested that the use of a polar cleaning solution will neutralize and solvate residual counterions from the charge control and stabilizer present in the liquid developer. This method is somewhat time consuming and impractical (the '387 patent discloses "washing the developed image after each development step and before applying the next developer .... After washing and drying. , Wipe or otherwise remove the cleaning liquid from the photoconductive element ... ".
Column 2, lines 62-67).

The present invention provides a novel method for controlling the charge of a liquid electrophotographic developer composition to address the above problems. The invention presupposes the formation of a very stable charge control agent / toner complex, which in turn provides a very stable developer composition with very high particle-mediated conductivity and charge. The method and related compositions provide a simplified development method and allow for the preparation of very good quality electrophotographic prints.

Background technologyRMSchaffert et al., Electrophotographic processing,
generally; Electrophotography (London: Focal Press, 1
975) provides a comprehensive overview of electrophotographic methods and techniques. Representative documents relating to the field of color electrophotography include, among others, Greig U.S. Pat.
No. 21, Smith et al., No. 3,253,913, Neber No. 3,285,837
No. 3,337,340 of Matkan, and 3,553,093 of Putnam et al.
No. 3,672,887, Matsumoto et al., No. 3,687,661 of Sato et al.
No. 3,849,165 of Stahly et al. References describing electrophotographic toners and developers include Santilli U.S. Pat. No. 4,659,640 to Wielicki (which describes developer compositions containing dispersed waxes).
No. 2,986,521; Bartoszewicz et al. No. 3,345,293, Mi
No. 3,406,062 of chalchik, No. 3,779,924 of Chechak,
And No. 3,788,995 of Stahly et al.

Charge control agents: References on charge control agents include van de
r Minne et al., U.S. Pat. No. 3,012,969 (polyvalent metal organic acids combined with oxygen-containing organic compounds); Roteman et al.
No. 3,411,936 (metal soaps), Beyer No. 3,417,019 (metal soaps and organic surfactants), Stahly et al. No. 3,788,99
No. 5 (various polymeric drugs), Merrill et al., No. 4,170,563.
(Phosphate) and 4,229,513 (quaternary ammonium polymer), Ng 4,762,764 (polybutene succinimide, lecithin, basic barium petroleum sulfonate,
And mixtures thereof), and Research Disclosure, 6
Page 6, May 1973 included.

Image tinting in continuous toning: described in section above
Alexandrovich et al. U.S. Pat.No. 4,701,387 and Matkan
U.S. Pat. No. 3,337,340 is relevant insofar as each of these references relates to the problem of image coloring in continuous toning.

Toner resin: Sato et al., U.S. Pat. , Dried oil-modified alkyd resin,
And the use of a thermosetting binder resin such as a catalyst cured epoxy ester resin. Checha
U.S. Pat. No. 3,779,924 to k describes alkyd and modified alkyd resins (eg, soybean oil-modified and linseed oil-modified alkyd), and phenolic and modified phenolic resins (phenol-formaldehyde resin and its derivatives). . Kiriu et al. In U.S. Pat.No. 4,845,003 include acrylic resin, styrene-
It describes the use of butanediepoxy resins and polyester resins. Bartoszewicz et al. U.S. Patent No.
No. 3,345,293 describes rosin-modified phenol-formaldehyde resins, polystyrene-based resins and epoxy resins. US Patent No. 3,411,936 to Roteman et al. Describes a "substantially uncharged" (column 2, line 70) resin binder. Stahly et al., U.S. Pat.No. 3,788,99
No. 5 describes a toner resin containing a polar moiety such as sulfoalkyl acrylate and sulfoalkyl methacrylate. U.S. Pat. No. 4,229,513 to Merrill et al. Describes a halogenated polymer designed to act as a negatively charged binder resin. U.S. Pat. No. 4,762,764 to Ng et al. Describes thermoplastic toner resins such as poly (methyl methacrylate), poly (methyl acrylate), and poly (ethyl methacrylate).

Surface-Bound Polymers: U.S. Pat.No. 4,925,766 to Elmasry et al. Discloses that an ion-exchange polymer binds to the surface of A developer composition is described that is apparently designed to form. Elmasry et al., U.S. Pat. No. 4,946,753, also describes such ion exchange resins used in combination with toners.

DISCLOSURE OF THE INVENTION Accordingly, a primary object of the present invention is to overcome the above-mentioned disadvantages of the prior art.

It is another object of the present invention to provide a solvation-based method for imparting charge to toner particles in a liquid electrophotographic developer composition.

Yet another object of the present invention is a solvation-based method for imparting charge to toner particles in a liquid electrophotographic developer composition, wherein the selected metal is used as a charge control agent. It is an object of the present invention to provide a method comprising introducing a substance containing a specific solvation site effective for solvating a salt into a resin phase of toner particles.

Still another object of the present invention is to provide a toner to be introduced into a liquid electrophotographic developer composition,
Here, the toner is prepared with a resin phase containing a substance having such a specific solvation site.

Still another object of the present invention is to provide a liquid electrophotographic developer composition containing such a toner and a charge control agent dispersed in an insulating carrier body liquid.

Other objects, advantages and novel features of the invention will be set forth in part in the description of the invention that follows, and in part will be obvious to those skilled in the art upon a review of the following.
Or, it can be learned by practicing the present invention.

The above objects are accomplished in accordance with the present invention by providing a solvation-based method for imparting charge to toner particles in a liquid electrophotographic developer composition. This method is conditioned on being used in a very stable solvated toner particle / charge control agent complex. Charge control agents (see, for example, Schaffert, supra, pages 564-566).
In contrast to conventional methods in which toner particles are charged by simple adsorption, proton transfer, or ion exchange, the method of the present invention involves solvation, i.e., where the complex of charged toner particles is Formed by solvation. This is accomplished by introducing a substance containing a particular solvation site into the resinous phase of the toner. The metal salt acting as a solvation site and a charge control agent forms a very stable charged toner complex, i.e., a complex of (i) the cationic metal component of the charge control agent and (ii) the toner particles. To be selected.

Against this background, the solvation of cations such as metal ions is characterized by the formation of a known aquo complex as follows: M ^{+ n} + (r) H ₂ OM ^{+ n} (H ₂ O) _r (1) The exothermicity of complex formation, ie the formation constant, is related to the enthalpy of hydration (Table 1, item (B) of the detailed description)
See). Accurate thermodynamic values are not easily obtained with alcohols, carboxylic acids, etc., but there are parallel correlations. As a result, when connecting the toner particles and a specific charge control agent, equilibrium, such as seems to be applied ^{following: MXM + + X - (2} ) Here, X ⁻ is a counter ion, and T is a toner particle. This reaction is an equilibrium of hydration of metal ions from the gas phase. That is, the complexing (that is, charge control) reaction is promoted in a low dielectric solvent by solvation with a site on the surface of the toner particles. The most preferred solvation reaction is
It is characterized by a large exotherm and a large negative enthalpy. Considering the following formula, As the enthalpy of solvation becomes increasingly negative, the equilibrium constant K of the solvation reaction increases. In other words, the formation of solvation complexes becomes increasingly favorable.

When ionization sites are used on the toner particles, the reaction described in equation (3) may actually proceed according to the following equation: Then, the conductivity of the developer is lost, resulting in instability. As described in more detail below, the addition of a conjugate acid of the counterion suppresses this development and stabilizes the developer.

In a preferred embodiment, the resinous phase of the toner is prepared to include a polymer having a solvation site as described above, which is then present on the surface of the toner particles;
Once exposed, it can be used to solvate the charge control agent in the liquid developer. In other embodiments, the resinous phase of the toner is prepared to include a monomeric species having such a solvation site that may or may not be present in association with the solvating polymer. Regardless of whether the solvation sites are present on the monomeric species, the polymeric species, or both, preferred solvates maximize the stabilization of the resulting charged toner complex and provide a non-associated free charge control agent in solution. It must be emphasized that the cationic component of the charge control agent can be exothermically solvated to minimize the presence of Solvation can occur without substantial ionization of the solvation sites.

In another aspect of the present invention, there is provided a toner comprising, as described, a substance containing a specific solvation site in its resin phase.

In yet another aspect of the present invention, there is provided a developer composition comprising such toner particles dispersed in an insulating carrier liquid together with a selected metal salt acting as a charge control agent.

Yet another aspect of the invention is a process for making the toner and developer compositions described above, a continuous toning process utilizing solvation-based charge control, and the method and compositions described in detail herein. And an electrophotographic image comprising a composite color print prepared using

DETAILED DESCRIPTION OF THE INVENTION A. Definitions: As used herein, "toner" refers to resinous colored particles ("resin") that ultimately form an electrophotographic image on a photoconductive (pc) surface. In this specification, it is also referred to as “toner particles”.

As used herein, "development composition" refers to a dispersion of a toner and a charge control agent in a selected insulating carrier liquid. The developing composition may also contain many additional compositions described below.

“Particle-mediated” conductivity and charge refers to the charge, rather than being derived from free, non-associated salts (ie, non-associated charge control agents or other ionizable species) that may be present in solution. Substantially all conductivity and charge in the developing composition derived from the toner particles. The developing compositions of the present invention exhibit very high, particle mediated conductivity and charge, and very low continuous phase conductivity.

As used herein, "continuous toning" refers to a charging and developing process using two or more colors (as outlined in the background section above) to provide a multi-color final image. Means an electrophotographic development process, including repetition. This process is also referred to herein as "continuous multicolor image development."

"Background staining" is a problem that can occur in any electrophotographic process. The term as used herein has the meaning understood in the art and refers to the problem of unintentionally uncharging non-image areas where toner appears.

"Image staining" is a problem specific to continuous toning and, as used herein, has a meaning similarly understood in the art. This problem means that the colors of the initial color image in areas where the initial image should have been discharged but not discharged are overtoned by the second or subsequent process. "Image coloring" is also referred to herein and in the art as "character staining".

"Specific solvation site" refers to a moiety that is present in the material contained within the toner resin and is effective at solvating one or more metal salts that function as a charge control agent. "Solvation" in the conventional sense refers to the association or binding of a solute unit (in the present case, a charge control agent) and a solvent species (here, a solvation site on the toner surface). . For example, The McGraw-Hill Encyclopedi
a of Science and Technology, New York: McGraw-Hil
See l, 1987. As discussed herein, solvation encompasses chemical or physical interactions, or both, and ranges from loose complexes to well-defined, rigid complex structures. In the present invention, the solvation sites in the charge control agent are preferably selected to be an exothermic process in which the charge control agent is solvated, resulting in extremely stable, charged toner particles.

As used herein, "carboxyl" refers to the carboxylic acid moiety -COOH.

B. Summary of the New Method: As noted above, the focus of the present invention is on a solvation-based mechanism that imparts charge on toner particles contained in a liquid electrophotographic developing composition.

The present invention therefore encompasses a novel method of producing a very stable charge control agent / toner complex. As described in co-pending U.S. patent application Ser. No. 07 / 464,896, referenced above, the stability of the charge control agent / toner complex is of paramount importance in liquid electrophotography. I know there is. In the '896 application, the focus was on the use of toners containing surface ion exchange sites that were effective in forming extremely stable ionic complexes with metal salts that functioned as charge control agents. In the present application, the focus is on the solvation interaction, ie the cationic metal component of the charge control agent is complexed to the surface of the toner particles via solvation. As described in the '896 application, the toner and the cationic component of the charge control agent are:
As described herein, where complexation between the two components is highly advantageous, the charge control agent is present in substantially all complexed form and substantially in the solvent. No non-associated charge control agent is present. In the case of the present invention, the solvation site and the charge control agent are chosen so that a very stable complex results, as is a high solvation exothermic process. Examples of specific toner substances and charge control agents that can be used in this manner and provide very stable charged toner particles are listed in section (c) of this section.

Generally, the solvation sites can be derived from one or more monomer species mixed into one or more polymers and / or toner resins. In fact, the toner resin itself can be a polymer containing the desired solvation sites. A good solvation site, as described above, is one that does not ionize to a significant degree under normal storage and use conditions of the liquid electrophotographic developer. When an ionizable solvation site is present, for example, when a carboxyl group is present,
As described in the next section, the charge control agent is preferably either a pH neutral salt (ie, a metal salt of a strong acid) or a salt containing a self-stabilizing counterion. Also, if such an ionizable moiety is used as a solvation site, a small amount of an acid, preferably a counter-ion acid form of the charge control agent, may be used to equilibrate toward the non-ionized form of the species. Preferably, it is added to the developing composition (in the case of carboxyl groups, the added acid will generate COOH groups for the ionized COO 2 ^- species).

The charge control agent should also be selected with a view to maximizing the stabilization of the "solvated" charged toner particle complex. In particular, the charge control agent should be a metal salt containing a metal ion that produces a highly exothermic solvation interaction with the solvation sites described above. Suitable metals are generally
It has a large negative enthalpy of hydration. The following table shows the enthalpies of hydration of some ions: (FACotton and G. Wilkinson, Advanced Inorganic
Chemistry, New York: John Wiley & Sons, 1972) The present invention includes solvation by substances other than water, and thus does not include hydration itself. However, solvation enthalpies generally correlate with hydration enthalpies. The enthalpy of solvation herein (ie, the solvation of the cationic metal component of the charge control agent by the solvation site) is generally a large negative value (ie, the solvation reaction is about -50 kJ / Mol or less, preferably about -100 kJ
/ Mol, most preferably less than about -500 kJ / mol solvation enthalpy). As can be inferred from the table above, small, highly charged metal ions cause the most exothermic hydration or solvation reactions. (CRC
See Handbook of Chemistry and Physics, 67th Edition, page F-157. Therefore, such metals are preferred charge control agents for use in the present invention.

By alternately selecting a toner solvation site and a charge control agent that results in a very stable toner / charge control agent complex, (1) substantially all solution conductivity and charge is derived from the toner particles. (2) the liquid developer composition can be prepared in which the charge of the toner is highly stabilized, that is, the charge is retained for a long period of time, and (3) the toner particles themselves are highly charged. .
Throughout this application, as will be emphasized, these features result in very good quality final images, e.g., in image density, edge accuracy, etc., and remain in conventional, unnecessary "non-image" areas. This toner can be used in a continuous color process without having to perform an intermediate processing step required to remove the toner.

C. Novel Toner and Developer Compositions: In addition to the methods described above, the present invention encompasses new toner and developer compositions. The new toner is useful for formulating liquid developer compositions, where both conductivity and charge are substantially particle mediated, as described above. As currently available toner compositions, the toner of the present invention comprises (a) resin and (b)
It includes two basic components, a colorant. However, unlike prior art toners, the present invention, as described above, involves mixing a substance containing a particular solvation site into the resin phase of the toner particles.

As mentioned in the above section, the substances that can be mixed with the resin phase of the toner particles may include monomers, polymers, or both.

Preferred types of monomers include sulfhydryl groups, amines, or oxygen-containing moieties such as hydroxyl groups, carboxyl groups, ketones, amides and ethers.
It has a polar portion as a solvation site.
However, hydroxyl-containing monomer species are the best. Examples of monomer species that can be incorporated into the toner resin to provide such a specific solvation site include sugars such as mannitol, sorbitol, xylitol.

In the present invention, it is generally preferred that the substance containing a specific solvation site is a polymer. Preferred polymers, like the preferred monomers, are those that contain, as specific solvation sites, hydroxyl groups, sulfhydryl groups, carboxyl groups, ketones, amides, ethers, and / or amines. Examples of classes of polymers useful in the present invention that contain a chiton moiety as a particular solvation site include acrylates. An example of an amide-containing polymer is nylon, while an example of an ether-containing polymer is polyethylene oxide. Examples of the amino-containing polymer used in the present invention include polyvinyl pyridine. Examples of particularly preferred polymers for use in the present invention include ethylene-
Examples include acrylic acid copolymers, ethylene-vinyl alcohol copolymers, styrene-allyl alcohol copolymers, cellulose acetate-butyrate copolymers, hydroxyalkyl acrylate copolymers, and ionomers and mixtures thereof. However, as long as solvation of the charge control agent is possible and a detrimental interaction with any of the other components of the developer composition occurs, a highly stable toner / charge control agent complex is obtained. Those skilled in the art will recognize that a wide range of polymeric materials can be used, unless otherwise specified.

In general, a material containing a particular solvation site will be deionized under the conditions used in electrophotographic developers, ie, at least 80%, preferably at least 90%, and most preferably at least 95% of the solvation site. It is preferably not ionized under normal conditions of storage and use. Further, when the solvation site is of a type that can be easily ionized again, such as a carboxyl group, as described above, the developer composition further contains an acid to suppress ionization of the carboxyl group. Is preferred. Typically, this involves adding an acid form of the counterion of the charge control agent. For example, if the counter ion of the charge control agent is diisopropyl salicylate (DIPS), then add a sufficient amount of diisopropyl salicylic acid to
The equilibrium is at a point where the carboxylic acid groups are in a substantially non-ionized form.

As described below, in order to ensure the formation of a stable toner / charge control agent complex, the metal ions acting as the cation component of the charge control agent must be exothermically solvated by the above materials into aluminum. , Magnesium, chromium, iron and the like are also desirable. Preferred materials have very large negative values of enthalpy of hydration, and therefore, in the present invention, are about -500 kJ / mol or less,
Preferably, they provide an enthalpy of solvation of -1000 kJ / mol or less. Such values result in very stable charged toner complexes, which in turn allow for the preparation of liquid developer compositions having a virtually infinite shelf life. This aspect of the invention is a significant advantage over currently available developer compositions that are relatively unstable and have a limited shelf life.

Colorants that can be used in the toner include virtually any pigment, dye, or stain that can be incorporated into the toner resin and that is effective in rendering the electrostatic latent image visible. Examples of suitable colorants include: as a cyan colorant,
Phthalocyanine Blue (CI74160), Dian Blue (D
iane blue) (CI21180), Milori blu
e) (same inorganic pigment as ultramarine); as magenta colorant, Brilliant Carmine 6B (CI1585
0), quinacridone magenta (CI Pigment Red 12
2) and thioindigo magenta (CI73310); Benzidine yellow (CI21090 and CI21100) and Hansa yellow (CI11680) as yellow colorants;
Organic dyes; and carbon black, charcoal, and finely divided carbon, iron oxide, zinc oxide,
Titanium dioxide and the like can be mentioned. It should also be noted that the polymers used in the present invention tend to dissolve the above-mentioned pigments and dyes easily and are therefore very advantageous in this regard.

The developer composition of the present invention, as described above, together with the selected charge control agent, was dispersed in an insulating carrier liquid,
Contains the above toner.

One class of metal salts useful as charge control agents in the present invention is U.S. Patent Application No. 07/4, filed January 16, 1990.
No. 64,896, incorporated herein by reference. These charge control agents contain, as a counterion, an intramolecularly stabilized anion of an orthohydroxy aromatic acid, such as salicylic acid or a derivative thereof. By the term "derivative" of salicylic acid, Applicants have determined that one to four selected from the group consisting of lower alkyl (1-6C), lower alkoxy (1-6C), halogen, amino, hydroxy, nitro and sulfonate. Pieces, typically 1
It is also intended to include salicylic acid substituted with one to two substituents.

These charge control agents are typically of the formula (RO ⁻ ) _x M ^{+ n} (A
A ^-) can be represented by _y, however, M is a metal atom, AA ^-
Represents an anion of an ortho-hydroxy aromatic acid, R represents is selected from the group consisting of R'CO-, C ₁ -C ₁₅ alkyl,
n is 2, 3 or 4, and x and y are integers whose sum is clearly n. The metal atoms "M" can be divalent, trivalent or tetravalent, and those metal atoms that bind most strongly to the toner resin are preferred. (In one particularly preferred embodiment, AA ^- is diisopropyl salicylate (DIPS) and R is C ₁₀ H ₂₁ CO- (ie, R ′
Is C ₁₀ H ₂₁ ), n is 3, x is 1 or 2, and y is 1 or 2.

A second class of charge control agents useful in the present invention is described in detail in US patent application Ser. No. 07 / 546,044, which is incorporated herein by reference. These charge control agents are of the formula (X ⁻ ) _a M ^{+ n} (AA ⁻ ) _b , where M
Is the above-mentioned metal atom, AA ^- is U.S. Patent Application No. 07/46
Represents in which anion of the ortho-hydroxy aromatic acid as described with respect to the charge control agent No. 4,906, X ^- is alpha, represents an anion of β- diketone, n is 2, 3 or 4, a
And b are integers whose sum is equal to n, provided that neither a nor b is 0.

As described in US patent application Ser. No. 07 / 546,044, the anion X ⁻ is an anion of an α, β-diketone, preferably of the formula: It represents what has. With the proviso that R ¹ and R ² are each independently selected from the group consisting of hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, haloalkyl, allyl, alkaryl, and haloallyl. Alkyl,
For alkenyl, alkynyl, cycloalkyl, or haloalkyl, the substituents are preferably about 1 to about 12
Carbon atoms, more preferably from about 1 to about 6 carbon atoms (the latter moiety is referred to herein as "lower"
Alkyl, alkenyl, alkynyl, etc.). In the case of allyl, alkaryl, or haloallyl, the substituents preferably contain 1 to about 3 rings, more preferably 1 to 2 rings, and are most preferably monocyclic.
An example of a particularly suitable α, β-diketone is acetylacetone, ie, R ¹ and R ² are both methyl.

The developer composition of the present invention comprises a toner and a developer dispersed in an electrically insulating carrier liquid well known in the art. The liquid is typically lipophilic, stable under various conditions, and electrically insulating. That is, the liquid has a low dielectric constant and a high electrical resistivity, and therefore does not interfere with the development of the electrostatically charged pattern. Preferably, the carrier liquid is about
3.5 or less, more preferably has about 3 or less dielectric constant, about ¹⁰⁹
It has a melt resistivity higher than ohm-cm, more preferably higher than about 10 ¹⁰ ohm-cm. Examples of suitable carrier liquids are carbon tetrachloride, halogenated hydrocarbon solvents such as trichloroethylene, and, for example, trichloromonofluoromethane and trichlorotrifluoroethane (DuPont Compa
fluorinated alkanes such as cyclohexane, n-pentane, isooctane, hexane, heptane, decane, dodecane, tetradecane, etc .; benzene ,
Aromatic hydrocarbons such as toluene, xylene, etc .; silicone oils; molten paraffin; and Isopar G, Isopar
H, Isopar K, Isopar L (trademark of Exxon Corporation)
Includes paraffinic hydrocarbons sold under the trade name The above list is merely illustrative of the carrier liquids that may be used in the present invention, and is not intended to be limiting.

C. Production of toner and developer: The toner is prepared by mixing the resin and the colorant at an elevated temperature, followed by dry grinding. Thereafter, the intermediate particles supplied in this way are subjected to liquid abrasion (liquid a
ttrition) to obtain the final toner particles. The following is an example of such a process: The resin and colorant are mixed at a temperature ranging from about 70 ° C to 200 ° C. Mix thoroughly using a two-roll mill, extruder, or high-power mixer. Thereafter, the mixture is dry-milled, i.e., milled without the addition of liquid, to provide intermediate particles typically having a diameter of 30 mils. This drying and pulverizing step is performed in a jet mill, a hammer mill, or the like. Thereafter, the intermediate particles thus obtained are subjected to liquid abrasion in a selected abrasion liquid to obtain final toner particles. The liquid used for attrition is typically selected from the same types of liquids that are useful as carrier liquids for the developer composition, as described below.

The composition of the developer of the present invention--prepared by dispersing the toner and the charge control agent in an insulating carrier liquid--is preferably mixed with the toner at an early stage of the process, i.e., step (A) may contain additional substances to be mixed with the colorants, resins and the like, for example, an incompatible phase such as wax (see related application no.
07 / 464,896). Developers may also include anti-coloring agents to mitigate background coloring problems, as described in the parent application of the present application. The anti-colorant is preferably
It is mixed with the composition at the stage of toner production. The developer composition may also include other materials well known in the art, for example, dispersants, stabilizers, and the like.

D. Continuous Multicolor Image Development: The continuous multicolor image development step (or "continuous toning step") using the materials of the present invention is performed briefly as follows.

The surface of the photoconductive insulating layer on a relatively conductive substrate is charged and an initial electrostatic charge pattern (or "latent image") is formed on the surface by exposure through a colored transparent member. . Thereafter, the latent image is developed with a first color liquid developer composition, ie, a composition including a first colorant, typically a toner dispensed in yellow. afterwards,
The photoconductive layer is discharged optically or non-optically, ie by corona. Then, these steps, different colors,
Typically (in order), the sequence is repeated with magenta, cyan and black developer compositions. At that point, the developed image can be transferred to another substrate, such as paper, if desired. Using the toner and developer compositions of the present invention, i.e., a composition that includes a solvation interaction between the surface of the toner particles and the mixed charge control agent, allows any intermediate steps to be performed, i.e., washing, drying, etc. The above steps can be performed continuously without performing the above. These steps are typically performed by Alexandrov, who addressed the issue of image coloring described above.
This was necessary in the prior art exemplified by the Ich et al. patent.

As shown by the above disclosure and the following examples, the compositions and processes of the present invention address and overcome significant obstacles previously encountered in color electrophotographic imaging.

The following examples illustrate the preparation and use of materials used in the compositions and processes of the present invention.

Example 1 RJ-100 (Allied Chemical Co., Morristown, New Jerse)
Styrene-allyl alcohol copolymer obtained from y)
Was melted at 95 ° C. on a double roll mill. To the molten polymer was added 32 g of Heliogen Blue, 3 g of Pigment Green 7, and 0.9 g of Sicofast Yellow D-1155. Stirred for 30 minutes, at which time 10 grams of carnauba wax was added. After further mixing for 15 minutes, the mill was cooled and the resulting product was removed. The mixture was ground at low temperature on a hammer mill. 30 g of this powder, Iso
The grinder was filled together with 130 g of parG (Exxon). 45 minutes later,
After the pulverization was completed, the pulverizer was removed from the pulverizer and diluted with 130 g of Isopar to obtain a 10% concentrate.

IsoparG was added to 40 g of the above concentrate and diluted to 400 g,
The used developer was 1%. 0.4 g of 1% -aluminum diisopropyl salicylate was added to the developer used. The developer prepared in this way exhibited a stable conductivity of 4.1 pmhos and an excellent shelf life. This positively charged developer produced a sharp, dark image on the ZnO photoconductor.

Example 2 The procedure of Example 1 was repeated, except that RJ-100 was replaced with ACX 260, an ethylene vinyl acetate / vinyl alcohol copolymer (obtained from Allied Chemical Company). Essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 3 The procedure of Example 1 was repeated except that the charge control agent used instead of aluminum diisopropyl salicylate was chromium octoate. Essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 4 The procedure of Example 1 was repeated except that the charge control agent used in place of aluminum diisopropyl salicylate was aluminum tri-neodecanoate (Mooney Chemical). Essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 5 The procedure of Example 1 was repeated except that the charge control agent used instead of aluminum diisopropyl salicylate was copper octoate (Mooney Chemical). Essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 6 The procedure of Example 1 was repeated except that the charge control agent used in place of aluminum diisopropyl salicylate was iron octoate (Mooney Chemical). Essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 7 The procedure of Example 1 was repeated, except that the charge control agent used in place of aluminum diisopropyl salicylate was aluminum dinonyl naphthalene sulfonate. Essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 8 The procedure of Example 1 was repeated except that the charge control agent used in place of aluminum diisopropyl salicylate was Al (AcAc) (DIPS) ₂ , where "AcA
"c" stands for acetylacetonate and "DIPS" stands for diisopropyl salicylate. Essentially similar results were obtained in terms of stable conductivity, shelf life and image quality.

This charge control agent was prepared as follows. Aluminum acetylacetonate (Aldrich Chemical Company,
6.4 g; 0.2 mL) and 8.88 g of diisopropylsalicylic acid (Aldrich Chemical Co.) were dissolved in 100 g of toluene. The solution thus obtained was heated at 95-100 ° C for 2 hours. The solvent was distilled off in vacuo at 95 ° C. (steam bath), leaving 11.3 g of viscous glass. The residue was dissolved in 25 mL of heated acetone. Upon distilling off the acetone in vacuo, a friable millet was formed, which was dried at 70 ° C. for 24 hours. The product C ₃₁ H ₄₁ O ₈ Al, [Al (AcAc) (DI
PS) ₂ ], the theoretical percentage of Al was found to be 4.75 compared to 4.75. The product was readily soluble in Isopar and gave the toner a positive charge at a rate of 10 ^-7 -10 ^-5 mol / g toner.

Using the process described in Example 1, essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 9 175 g of ACX 251 (ethylene-vinyl alcohol polymer obtained from Allied Chemical Co.) was melted at 90 ° C on a double roll mill. To the molten polymer, 31.4 g of Heliogen-L 7080, 2.9 g of Heliogen Green (Picture Green 7), 0.8 g of Sicofast D-1155, and 6.6 g of WB-11, a cationic wax dispersant (Petrolite), are added. Was. Stirring was performed for 30 minutes. The mill was cooled and the product was removed and processed to a 10% concentrate as described in Example 1.

To 400 g of the 1% used developer was added 0.6 g of a 1% solution of aluminum tri-neodecanoate ((Mooney Chemical)) with a conductivity of 7.8 pmhos. Lifespan was very good: the positively charged developer gave excellent, dense,
Generated high resolution images.

Example 10 The procedure of Example 9 was repeated except that the charge control agent used instead of aluminum tri-neodecanoate was aluminum diisopropyl salicylate. Essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 11 The procedure of Example 9 was repeated except that the charge control agent used in place of aluminum tri-neodecanoate was zirconium dineodecanoate (Mooney Chemical). Essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 12 The procedure of Example 9 was repeated except that the charge control agent used in place of aluminum tri-neodecanoate was iron tri-naphthenate (Nuodex). Essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 13 The procedure of Example 9 was repeated except that the charge control agent used in place of aluminum tri-neodecanoate was Al (AcAc) (DIPS) ₂ , where "AcAc" and "DIPS" were As defined above. This charge control agent was prepared as described in Example 8.

When used in the process described in Example 8, essentially similar results were obtained in terms of stable conductivity, shelf life, and image quality.

Example 14 120 g of AC 201 resin (Allied Chemical) was placed on a double roll mill at 100 ° C. Sicofast D for molten polymer
52 g of -1155 were added. After stirring for 30 minutes, 60 g of AC 540 resin (Allide) and 60 g of AC 7 (Allide) were added. After stirring for 15 minutes, 10 g of Ethomid HT 60 dispersant (obtained from Akzo) and 13 g of WB-17 dispersant (Petrolite) were added. Stirring was continued for 20 minutes, and the product was removed and 10% as described in Example 1.
To give a concentrate.

To 400 g of the 1% working developer was added 1 g of a 0.05% solution of aluminum or diisopropyl salicylate and 2 g of a 1% solution of diisopropylsalicylic acid. Its conductivity is 3.7p
mhos. This developer, which, like the developer composition of the previous example, exhibits excellent shelf life,
A sharp dark image was produced on the ZnO photoconductor.

Example 15 The procedure of Example 14 was repeated except that the charge control agent used in place of aluminum diisopropyl salicylate was Al (AcAc) (DIPS) ₂ , where "AcA
"c" and "DIPS" are defined above. The charge control agent was prepared as described in Example 15.

Essentially similar results when used in the process described in Example 30.

Example 16 Sicofast D-1155 was applied to Foster Palm Red (Ho
staperm Red) The procedure of Example 14 was repeated except that it was replaced by E5B-O2. Essentially similar results were obtained with respect to stable conductivity, shelf life and image quality.

Example 17 Sicofast D-1155 was obtained from Hariogenble-L-7080
The procedure of Example 14 was repeated except that was replaced by Essentially similar results were obtained with respect to stable conductivity, shelf life and image quality.

Example 18 Sicofast D-1155 was purchased from Nova Palm Yellow (Nova
perm Yellow) The procedure of Example 14 was repeated except that it was replaced by FGL. Essentially similar results were obtained with respect to stable conductivity, shelf life and image quality.

Example 19 Sicofast D-1155 is Indofast Brilliant scarlet R-63
The procedure of Example 14 was repeated except that it was replaced by 35. Essentially similar results were obtained with respect to stable conductivity, shelf life and image quality.

Example 20 Sicofast D-1155 was purchased from Quind Magenta
Magenta) The procedure of Example 14 was repeated except that it was replaced by RV6832. Essentially similar results were obtained with respect to stable conductivity, shelf life and image quality.

Example 21 Sicofast D-1155 was purchased from Quind Re
d) The procedure of Example 14 was repeated except that it was replaced by 6713. Essentially similar results were obtained with respect to stable conductivity, shelf life and image quality.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-285364 (JP, A) JP-A-56-10619 (JP, A) JP-A-50-125743 (JP, A) JP-A-61-1986 279866 (JP, A) JP-A-62-34170 (JP, A) JP-A-60-121458 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/13

Claims (14)

(57) [Claims] 1. A method for imparting a positive surface charge to toner particles used in a liquid electrophotographic developer composition, comprising: (a) a colorant in a lipophilic electrically insulating carrier liquid; (B) a charge controlling agent containing a metal salt having a metal ion selected from aluminum, chromium and iron; wherein the resin phase is a complex with a metal ion of the metal salt. Comprising a monomeric or polymeric material having a specific polar group solvation site, and comprising a solvation site comprising a hydroxyl group or a carboxylic acid moiety -COOH, the charge control agent and the specific solvation site. Are selected such that their solvation by the substance is an exothermic reaction having a ΔH of -50 kJ / mol or less, whereby the metal ion forms a solvation complex with the hydroxyl group solvation site of the substance. Formed to; a method comprising the step of preparing a dispersion of, and wherein said solvation site comprises a carboxyl group,
And in the case of a developer composition wherein the amount of solvation sites that do not ionize during normal storage and use constitutes less than 90% of the solvation sites, the dispersion further comprises: (c) an ionization equilibrium of the carboxyl groups Comprising an effective amount of an organic acid to direct the compound to a substantially non-ionized form. 2. The method according to claim 1, wherein said substance is ethylene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, styrene-
Allyl alcohol copolymer, cellulose acetate-butyrate copolymer, hydroxyalkyl acrylate copolymer,
And the polymer selected from the group consisting of and ionomers and mixtures thereof. 3. The method of claim 1, wherein said charge control agent further comprises a salicylic acid anion or a salicylic acid derivative anion. 4. The method of claim 1, wherein the charge control agent further comprises, as a counterion, an anion stabilized in the molecule of an orthohydroxy aromatic acid. 5. The method according to claim 1, wherein said solvation site forming a complex with a metal ion comprises a solvation site comprising a carboxylic acid moiety -COOH, wherein said dispersion substantially reduces the ionization equilibrium of said carboxyl group. The method of claim 1, comprising an effective amount of an organic acid comprising the same anion as the anion of the charge control agent. 6. The solvation site forming a complex with a metal ion includes a solvation site consisting of a hydroxyl group, and the amount of the solvation site that does not ionize during normal storage and use is at least one of the solvation sites. Claim 1 comprising 90%
The method described in. 7. A positively charged toner complex formed when dispersed in a lipophilic, electrically insulating carrier liquid, comprising: (a) toner particles containing a resin phase containing a colorant; And (b) a charge control agent containing a metal salt having a metal ion selected from aluminum, chromium and iron; wherein the resin phase is a specific polar group solvent that forms a complex with the metal ion of the metal salt. Comprising a monomer or polymer material having a solvation site and comprising a solvation site consisting of a hydroxyl group or a carboxylic acid moiety -COOH, wherein the charge control agent and the particular solvation site Wherein the sum is selected to be an exothermic reaction having a ΔH of -50 kJ / mole or less, whereby the metal ion forms a solvation complex with the hydroxyl group solvation site of the material; The solvation site comprises a carboxyl group,
And in the case of a developer composition wherein the amount of solvation sites that do not ionize during normal storage and use constitutes less than 90% of the solvation sites, the dispersion further comprises: (c) an ionization equilibrium of the carboxyl groups An effective amount of an organic acid to direct the compound to a substantially non-ionized form. 8. A liquid developer composition for electrophotography, comprising: (a) toner particles containing a resin phase containing a colorant dispersed in a lipophilic electrically insulating carrier liquid; and (b) aluminum; A charge control agent containing a metal salt having a metal ion selected from chromium and iron; wherein the resin phase has a specific polar group solvation site forming a complex with the metal ion of the metal salt; And a solvation site consisting of a hydroxyl group or a carboxylic acid moiety -COOH, wherein the charge control agent and the particular solvation site are such that their solvation by the material is -50 kJ / mol. Wherein the metal ion forms a solvation complex with the hydroxyl group solvation site of the material, wherein the solvation site has the following ΔH: It includes a carboxyl group,
And in the case of a developer composition wherein the amount of solvation sites that do not ionize during normal storage and use constitutes less than 90% of the solvation sites, the dispersion further comprises: (c) an ionization equilibrium of the carboxyl groups An effective amount of an organic acid to direct the compound to a substantially non-ionized form. 9. The liquid developer composition according to claim 8, wherein said substance is a polymer. 10. The polymer according to claim 1, wherein the polymer is an ethylene-acrylic acid copolymer, an ethylene-vinyl alcohol copolymer, a styrene-allyl alcohol copolymer, a cellulose acetate-butyrate copolymer, a hydroxyalkyl acrylate copolymer, The liquid developer composition according to claim 9, which is selected from the group consisting of and ionomers and mixtures thereof. 11. The solvation site forming a complex with a metal ion comprises a solvation site consisting of a carboxylic acid moiety -COOH, wherein the dispersion substantially reduces the ionization equilibrium of the carboxyl group. 9. The liquid developer composition of claim 8, comprising an effective amount of an organic acid containing the same anion as the charge control agent. 12. The solvation site forming a complex with a metal ion comprises a solvation site consisting of a hydroxyl group,
9. The liquid developer composition of claim 8, wherein the amount of solvation sites that do not ionize during normal storage and use constitutes at least 90% of the solvation sites. 13. A method of developing an electrostatic charge pattern using a continuous toning system, comprising: (a) forming an initial negative electrostatic charge pattern on a substrate;
(I) resin particles of a resin phase containing a first colorant dispersed in a lipophilic electrically insulating carrier liquid; and (ii) a monomer comprising a metal ion selected from aluminum, chromium and iron Body charge control agent, a positively charged liquid developer composition containing
Developing the first pattern, then (b) forming a second electrostatically charged pattern on the substrate, dispersed in a lipophilic electrically insulating carrier liquid, (i) second coloring And (ii) a monomer charge control agent containing a metal ion selected from aluminum, chromium and iron, and a positively charged liquid developer composition comprising:
Developing the second pattern, wherein steps (a) and (b) are performed immediately and continuously without any additional method steps between the two, wherein the resin phase is A charge controlling agent comprising a polymer or monomeric substance having a specific polar group solvation site forming a complex with the metal ion, and including a solvation site comprising a hydroxyl group or a carboxylic acid moiety -COOH. And the particular solvation site is selected such that the solvation of the charge control agent by the substance is an exothermic reaction having a ΔH of -50 kJ / mol or less; and wherein the solvation site is a carboxyl group. Including
And in the case of a developer composition in which the amount of solvation sites that do not ionize during normal storage and use constitutes less than 90% of the solvation sites, the composition can (iii) increase the ionization equilibrium of the carboxyl group. Further comprising an effective amount of an organic acid to direct it to a substantially non-ionized form. 14. An electrophotographic image constituting a composite color print, wherein the electrophotographic image is deposited on a substrate in a predetermined pattern and includes the toner composite according to claim 7.